Large advances have been made in techniques to study human cortical function and its relationship to cognition. However, to know whether a certain area of the brain is not only sufficient but necessary to support particular cognitive operations, lesion studies are still required. The study of humans with lesions in targeted areas has the added importance of directly testing the cognitive sequela of brain damage, an increasingly frequent occurrence in an aging American population. Many studies that combine cognitive theory and methods with studies of neurological patients have demonstrated that the posterior cortex is extensively involved in object perception and visual spatial attention. Damage in these areas can cause severe problems in perceiving such features as shape, color, motion, location, etc. However, little is known about links between attention, object perception and memory and the neural mechanisms that support these links. The investigator recently found evidence for attentional and perceptual contributions to memory from spatial feature traces even when explicit memory was not required. These traces were altered in stable patients with focal lesions in the posterior cortex. In normals, features of attended objects seem to be automatically encoded and leave a trace for at least several seconds. These traces affect subsequent performance, but their duration is unknown. They are absent in groups of patients with left parietal lobe lesions. These traces could represent the elementary building blocks of memory that contributes to our knowledge of what features are critical in a selective task and how they are accessed. The proposed studies will extend investigation of these feature traces to issues in neuropsychology and cognitive neuropsychology. Studies are proposed to determine what features of unattended objects remain in memory, for how long, and under what conditions. The studies will help to determine the impact of cortical damage on these feature representations and the long-term functional consequences.